Resistance-grid.



W. H. KELLER.

RESISTANCE GRID. APPLICATION FILED JAN. 6. 1914.

1,184,706. Patented May 23, 1916.

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Specification of Letters Patent.

Patented May 23, 1916.

Application filed January 6, 191& Serial No. 810,545.

To all whom it may concern Be it known that I, WILLIAM H. KELLER,

a citizen of the United States, and resident of Norton, in the county ofWise and State of Virginia, have invented certain new and usefulImprovements in Resistance-Grids, of which the following is 'aspecification.

This invention relates to those electrical resistance units which are ofa -stifi' plate like character and have separated parts somewhatresembling a. grid iron,jso that they are known in the art as grids.

In using the resistance grids usually a plurality of them arev supportedin a suitable frame or on a suitable support, being suitably insulatedfrom each other and c0nnected together in desired relations, either inseries or in parallel, ora combination of the two systems. andconnecting grids is'well; understood in the art. The grids are usuallyclamped in position between end plates or screwed tightly. to a supportby means of screws passing into the feet of the grids, the conduc tivityof the electrical connection between the grids or from a'grid to aconnecting piece being dependent upon the secure clamping of the partstogether. Where cast iron or other brittle grids are tightly clampedthey are liable to break. They are also liable to breakage by beingaccidentally struck or by jarring or jolting, such as that to whichgrids'are sub ected upon electric locomotives or other vehicles.' Also,grids heretofore in use are liable to warp when hot, so that adjacentgrids of a rheostat may come together and short circuit a portion of theresistance unless the grids are placed so far apart that this contactcannot occur. 40 It will be apparent, however, that this will preventcompact construction of the rheostat and a compact construction iscertainly greatly to be desired, if not absolutely necessary, onlocomotives and Y space is valuable.

It is an object of the present invention to provide a resistance gridwhich shall be inexpensive to' manufacture, which shall answer thepurpose of a resistance unit efliciently, which shall not be liable tobe broken by jarring or jolting, which may. be clamped tightly to securegood electrical connection and secure support and which will not bewarped by the heating due to the passage of the electric current.

The objectof the invention is accom- The manner of mounting employed,

other places where I plished by providing a grid of iron of suflicientductility so that the grid may be stamped or cut by a die from ofsuitable thickness. Iron of the character referred to is found in thatclass of the metal known steel. ductilit etc., may be summed up in theword malleable. My experience in the matter has shown that steel ishighly preferable and possesses numerous advantages.

Grids of the character described may be tightened into good electricalcontact, are not broken by warp when hot and may be inexpensivelyproduced by punching by simple dies from plane sheets of metal. Themetalis not expensive, which permitsthe use of lar as wrought iron andalso in gegrids for carrying large quantities without alarge expenditureand at the same time an eflicient resistance unit is supplied. Also,this permits as a commercial proposition the use of a grid of suiiicientsize so that, taking into consideration the character of the metalconformation of id to accomplish this end.

e invention is illustrated in the accompanying drawing, of which- Figure1' is a side elevation of a rheostat including grids according to thepresent invention; Fig. 2 is an end view of the rheostat shown in Fig.1; and Fig. 3 is an en larged view of a grid according to the presentinvention, the manner of its mounting and insulation in the rheostat ofFig. 1 being indicated.

eferring to the drawing, which the grids are to be mounted comprises theend plates 0 and b between which extend the bolts 0, d and 0, havingnuts outside the ends of the plates as shown. Between the plates arearranged grids f.

The structure of a grid is shown best in Fig. 3, from which it appearsthat each grid comprises the reflexed portions 1, 2, 3, 4, 5 and 6, thusproviding a long path for the current in going from one side of the gridto the other; At one end of each of the outside grids is a hole throughwhich the bolts (1 and e pass, while at the middle of the grid upon theopposite side from the tioned is another hole through which is threadedthe bolt 0. The grid is ordinarily arring or knocking, will not it isself sustaining to a great extent and does not require any peculiarholes. men

a sheet of iron The desired qualities of pliability,

the frame in or bushings '7, 8 and 9, which envelop the bolts andadjustment grids may be insulated from each other where desired by meansof insulating washers as 10 and 11, which are interposed between thegrids and threaded upon the bolts. Preferably the insulating bushingsand washers referred to are made of mica, although other insulatingmaterial might be employed.

Each grid is punched from a sheet of steel of suitable thickness and allof the parts of the punched grid lie in a lane sheet. As noted above,other forms 0 iron than steel may be employed but do not realize all theadvantages to the same extent as the steel.

It will now be apparent that in order to farm the rheostat as shown inFigs. 1 and 2, t e bushings on the bolts d, c and'e, the plates a and bare placed on the ends and the nuts on the bolts are tightened so thatthe whole is clamped firmly together, insulating washers having beenplaced between the grids upon the bolts where it is desired to separatethe grids while such washers are omitted or metallic desired toestablish electrical tween adjacent grids.

The end plates (1. and b of the rheostat are provided with feet as 12and 13, through which screws or bolts may pass into the support, such asthe floor of a car, in order to secure the rheostat in position.

Electrical connection may be made to the grids in any of the ways wellknown in connection bethe art.

While the invention has been illustrated in what is considered its bestapplication, it may be embodied in various structures without departingfrom its spirit and is not rids are'threaded over the insulatingwashersinserted where it is therefore limited to the structure shown in thedrawing.

What I claim is:

1. In a 'rheostat, the combination with supporting rods, of a pluralityof reflexed resistance grids mounted thereon, means for clamping saidgrids toward each other endwise of said rods, means for spacing saidgrids along said rods so that air spaces are formed between them, andmeans for insulating said grids from said rods and each other at desiredpoints, each of said grids being punched from sheet steel and having thegreater portion of its surface exposed to the air.

2. In'a rheostat, the combination with a support, of a plurality ofreflexed resistance grids of sheet steel mounted thereon, said gridsbeing spaced apart so that air Spaces are formed between them, insulatedfrom each other at desired points and each having the greater portion 0.its surface exposed to the air.

3. In a rheostat, the combination with a sup ort, of a plurality ofreflexed resistance grl s of malleable metal consisting in the.

greater art of iron, mounted thereon, said grids being spaced apart sothat air spaces are formed between them and insulated from each other atdesired points, and each having'the greater portion of its surfaceexposed to the air.

Si ed at Norton, in the county of Wise, and tate of Virginia, this 31stday of December, A. D. 1913.

WILLIAM HENRY KELLER.

Witnesses:

R. B. COWAN, Geo. I]. Ro'rEBUcK.

